Pain at Higher Level: An AHL statement: how free nerve endings turn a stimulus into the feeling of pain.
Practise this as you read
- Describe how a stimulus leads to pain.
- State examples of pain stimuli.
Free preview
This is the free notes preview
You're reading the free notes. Aimnova Pro unlocks the full study experience — and you can try it with your first topic free to keep:
- FlashcardsLock in vocabulary and key terms with spaced repetition.
- Practice questionsAnswer exam-style questions and get instant AI marking.
- Mock exams & past-paper vaultSit full mocks and see exactly how examiners award marks.
- Personalised study planA daily plan built around your exam date and weak areas.
Start Studying Free Full access to Aimnova Pro · cancel anytime
The big idea: Pain is detected by sensory neurons with free nerve endings in the skin. A stimulus such as high temperature, acid or capsaicin from chilli peppers opens channels for positive ions. The ions enter, the threshold is reached, and nerve impulses pass to the brain, where the pain is perceived.
The points to remember
- Pain receptors are free nerve endings of sensory neurons in the skin.
- Stimuli: high temperature, acid, capsaicin in chilli peppers.
- Channels for positively charged ions open, and the ions enter.
- The threshold is reached: nerve impulses start.
- Impulses pass to the brain, where pain is perceived.
Remember it as: Open the channel, reach the threshold, tell the brain.
Real example: why chilli feels hot. Capsaicin, the chemical in chilli peppers, opens the same channels in the nerve endings that open at high temperatures. The brain receives the same kind of impulses, so a chilli feels burning hot even though nothing is hot.
Trap: The pain is perceived in the brain, not in the skin: the nerve endings only start the impulses.
Never wonder what to study next
Get a personalized daily plan based on your exam date, progress, and weak areas. We'll tell you exactly what to review each day.
Try Free Study PlanYour first topic is free to keep • No credit card required
How it is asked: Expect a Describe question on how a stimulus such as heat or a chilli pepper leads to the feeling of pain.
IB-style questionDescribe[3 marks]
Describe how eating a chilli pepper leads to a feeling of pain.
Model answer plan
See the answer broken into clear points, with guidance on how each point earns marks.